1. Field of the Invention
This invention relates to a magnetic disk, and more particularly to a magnetic disk employed in an electronic still camera and in a recording or reproducing system adapted to receive video signals for later recording on a recording medium or later visualization on a video monitor, for example.
2. Description of the Prior Art
On magnetic disks, heretofore, signals have been recorded in the form of either analog or digital signals.
For example, when testing or adjusting an analog reproducing apparatus for video floppies (VF), a signal representative of a reference or standard picture or image is required for comparison of the image quality reproduced. The reference image is reproduced both on a reproducing apparatus to be adjusted or tested and on some other reproducing apparatus so that the two reproduced images can be compared to each other for adjusting or testing the former reproducing apparatus. Therefore, the reference image or picture is required to be of as high a picture quality as possible. For obtaining such a high quality reference image, recording the image in the form of digital signals is preferred.
When the reference image is recorded in the form of analog signals, it can be reproduced more easily so that its contents can be determined promptly. However in the analog recording, as compared to the digital recording, the image quality tends to be undesirably lowered because of susceptibility to image signal distortion, so that it is difficult with analog recording to obtain a reference image of satisfactory image quality. In contrast thereto, in the case of recording by digital signals, while the reproducing apparatus itself becomes bulky and more sophisticated, a reference image of higher image quality may be produced.
It may be seen from above that digital signals are more preferably employed in recording a reference image to be used for testing or adjusting the analog reproducing apparatus for video floppies.